Portable electronic devices and wearable devices, such as cellular phones and smart watches, are useful for message-based communications. Exemplary message-based communications include the short message service (SMS), as well as iMessage technologies provided by Apple Inc., of Cupertino, Calif. The small form factors of portable electronic devices, however, present user interface challenges. One persistent challenge arises from the reduced-size input modalities typically employed by these devices, which are sub-optimal for typing. This difficulty is exacerbated by continued improvement in electronics packaging techniques that lend to smaller devices with even less room for keyboard placement. Techniques for suggesting content for insertion in messages—thereby reducing the need for manual user input—are thus desirable.